This invention relates to hand tools, and more specifically to a hand tool for cutting plastic pipe or tubing, rubber hose, or other similar non-metallic materials.
In recent years, the use of plastic pipe, plastic tubing and heavy wall rubber tubing has become widespread. These items have, however, presented some difficulty in cutting them in the field so as to achieve a straight and true cut. Due to the low hardness of plastic pipe or tubing, as compared with metal pipe, and due to the resiliency of the plastic, it was recognized that it should be possible to cleanly and quickly cut plastic pipe by means of a movable blade which closes on the pipe and pinches it between the movable blade and a stationary anvil or cutting jaw. However, the softness or compressibility of certain types of plastic or rubber pipe, the thickness of the plastic or rubber pipe to be cut, and the substantial cutting force required to sever many plastic or rubber pipes have posed major problems in the design of suitable plastic pipe cutters. Oftentimes the needs for exerting high cutting forces simultaneously with the need for exerting these cutting forces through a relatively large distance (for example in the case of cutting 11/4 inch (3.2 cm.) diameter plastic piping) have worked against one another. Oftentimes, a prior art plastic pipe cutter design would overcome one of these problems only encounter another.
Certain of the prior art plastic pipe cutters used a ratchet drive for moving a shear blade through its cutting stroke so that the operator could readily exert the high forces needed to sever the plastic pipe and so that the shear blade may be moved through the distance necessary to cut through the pipe. However, in cutting certain types of soft plastic pipe, such as polybutylene, the tendency of the pipe to spring back to its original shape upon opening of the handles of the prior art pipe cutters when operating the ratchet drive caused the cutting blade to move away from the pipe thus effectively preventing the cutter from cutting the pipe. In certain of the prior art plastic pipe cutters, it was necessary for the user of the tool to grip the shear blade and to hold it against opening upon operation of the ratchet drive. Of course, this unnecessarily increased the risk of injury to the user.
Also, most of the prior art plastic pipe cutters had an exposed shear blade (or sharp tips of the blade) which extended out beyond the anvil when the blade was closed thereby presenting a hazard to the user of the tool. Furthermore, the exposed blades were more likely to be damaged.
Still another difficulty with certain prior art plastic pipe cutters was that a great amount of force was required to be manually applied to the handle of the tool so as to sever the plastic pipe and the user often was required to use both hands to operate the tool. It is, of course, desirable that one handed operation of the tool be possible so as to permit the user to grasp the pipe being cut or to simultaneously perform some other task. Also, in certain of the prior art plastic pipe cutters, the release of the shear blade from its closed position was difficult and oftentimes required the use of both hands to open the tool.
Reference may be made to U.S. Pat. Nos. 3,273,240 and 3,390,455 which disclose shears for cutting thick tree branches or the like in which a movable shear blade is operated via a handle and ratchet mechanism. U.S. Pat. No. 4,084,317 discloses a plastic pipe cutter broadly similar to the pipe cutter of the present invention.
Among the several objects and features of this invention may be noted the provision of a cutting tool particularly well-suited for cutting plastic pipe, rubber tubing, or other articles (preferably non-metallic articles) which are crushable or otherwise somewhat elastic or compressible;
The provision of such a cutter which may be readily used for one-handed operation both for cutting the article and for opening the tool;
The provision of such a tool which allows the operator to easily apply the high cutting forces necessary to cut the article and yet to apply these high cutting forces over a considerable distance so as to accommodate articles of appreciable thickness;
The provision of such a cutter which readily accepts and cuts any diameter or thickness of article within a range of diameters or thicknesses and in which the blade may be readily and rapidly moved into cutting engagement with the articles;
The provision of such a cutter in which the blade may be retracted clear of the article being cut at any point in the cutting stroke of the blade or upon severing of the article;
The provision of such a cutting tool in which the blade, when retracted, is enclosed thereby to protect the blade from damage and to protect the user from injury; and
The provision of such a cutting tool which is easy and safe to use, which of rugged and economical construction, and which cleanly and quickly cuts a variety of articles.
Other objects and features of this invention will be in part apparent and in part pointed out hereinafter.